Timeline for Is it true that for Observer Pattern to work, there probably is some polling mechanism underneath?
Current License: CC BY-SA 3.0
13 events
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Dec 31, 2015 at 6:57 | comment | added | justhalf | Also I think the key here is that "listen" is different from "polling". Listening is passive, while polling is active. I can keep my ears ready to receive any message that my friend will speak, and receives it as soon as they speak, but this is not polling. | |
Dec 22, 2015 at 22:06 | comment | added | Winston Ewert | @太極者無極而生, yes. Otherwise, the computers you connect to could never respond. | |
Dec 22, 2015 at 22:05 | comment | added | nonopolarity | hm, ok, I think I just got tied down to the idea that I have to open a port in firewall or else it is not open... so it is in fact true that, once we established a TCP/IP connection, even in the presence of a firewall, the communication can now be 2-way? | |
Dec 22, 2015 at 5:54 | comment | added | Winston Ewert | The automatic firewall port opening depends on the program on your computer sending the first message. Once the first message is sent, then the firewalls opens. If you want another computer to send your computer the message first, then you need to manually open the port. | |
Dec 22, 2015 at 5:24 | comment | added | nonopolarity | hold on a second, I thought in some cases we would open up a port, or forward a port to a machine on the LAN, so if the app can let the data go through the firewall, why would we need to open up a port on the router? | |
Dec 22, 2015 at 5:11 | comment | added | Winston Ewert | The typical case in a firewall, would be that Trent also looks at the outgoing mail. He saw Bob send a letter to Alice. Since that happened, he doesn't destroy Alice's letter back to Bob. However, when Charley sends a letter to Bob, Trent destroys it because Bob never sent a letter to Charley. | |
Dec 22, 2015 at 5:09 | comment | added | ArTs | @太極者無極而生 However, if Bob then gives a letter to Trent, saying, "Please send this letter to my friend Alice". Then Trent is likely to let packages from Alice to Bob through. | |
Dec 22, 2015 at 5:07 | comment | added | ArTs | @太極者無極而生 Imagine your home is an army base. A truck turns up at the gate and tries to drop off a "packet" for Bob. Trent who works at the gate promptly destroys the package. | |
Dec 22, 2015 at 4:55 | comment | added | Winston Ewert | @SamiKuhmonen, as a computer scientist I'm not really sure that physical layer actually exists. | |
Dec 22, 2015 at 4:54 | comment | added | Sami Kuhmonen | You forgot photons, if you really want to go to the physical layer... | |
Dec 21, 2015 at 23:22 | comment | added | Winston Ewert | Actually, yes Dropbox can tell the firewall to open things up. When the dropbox client talks to the Dropbox server, the firewall automatically opens up the firewall so that the Dropbox server can talk back. Its going to be very restricted, only the exact same dropbox server can talk back, and only to the exact address that started the conversation. But it still does open up the ports that way. | |
Dec 21, 2015 at 23:14 | comment | added | nonopolarity | you said "because your computer was talking to dropbox, it doesn't deem the packet suspect, and thus forwards the packets on" but I never configured the firewall to let anything through... and I don't think Dropbox can tell the firewall to open up to let things go through | |
Dec 21, 2015 at 22:01 | history | answered | Winston Ewert | CC BY-SA 3.0 |